The possibility of orange pulp utilization for nanoporous carbons production was investigated. Moreover, processing the obtained materials as limonene oxidation catalysts was studied as well. Limonene was separated from orange pulp obtained from fragmented orange peels—the waste from industrial fruits processing—by means of simple distillation. After the separation of limonene from the biomass, the dried orange pulp was converted to three types of nanoporous carbon catalysts: without activating agent, with NaOH, and with KOH. The catalysts were characterized by XRD, SEM, EDX, AFM, and sorption of N2 methods. The activities of the obtained catalysts were tested in the oxidation of limonene to perillyl alcohol (the main product), carveol, carvone, and 1,2-epoxylimonene and its diol. In the oxidation processes, hydrogen peroxide was used as the oxidizing agent. This work has shown for the first time that nanoporous carbons obtained from orange pulp waste, after separation of limonene, are active catalysts for limonene oxidation to industrially important value-added products.

    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Preparation of catalysts from dried orange pulp residue (after limonene distillation)
        2.3 X-ray diffraction
        2.4 Nitrogen sorption
        2.5 SEM, EDX, and AFM analyses
        2.6 Method of limonene oxidation
    3 Results and discussion
        3.1 Catalyst characterization
        3.2 Oxidation of limonene with H2O2
    4 Conclusions
    Acknowledgements 
    References

• Agnieszka Wróblewska(Faculty of Chemical Technology and Engineering, Institute of Organic Chemical Technology, West Pomeranian University of Technology)
• Jarosław Serafin(Faculty of Chemical Technology and Engineering, Institute of Inorganic Chemical Technology and Environment Engineering, West Pomeranian University of Technology)
• Alicja Gawarecka(Faculty of Chemical Technology and Engineering, Institute of Organic Chemical Technology, West Pomeranian University of Technology)
• Piotr Miądlicki(Faculty of Chemical Technology and Engineering, Institute of Organic Chemical Technology, West Pomeranian University of Technology)
• Karolina Urbaś(Faculty of Chemical Technology and Engineering, Department of Nanomaterials and Physicochemistry, West Pomeranian University of Technology)
• Zvi C. Koren(Department of Chemical Engineering, Shenkar College of Engineering)
• Jordi Llorca(Institute of Energy Technologies, Department of Chemical Engineering, Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya)
• Beata Michalkiewicz(Faculty of Chemical Technology and Engineering, Institute of Inorganic Chemical Technology and Environment Engineering, West Pomeranian University of Technology)